Operation and maintenance problems in RO plant

One of the most important steps in maintaining the operation of the RO plant is to perform regular maintenance. This maintains the quality and longevity of the plant. Which reduces the cost and adds to its value over the years.

The maintenance engineer must know the common indicators by which he identifies the problem and thus facilitates finding the solution in a timely manner.

Discovering problems in the production of the desalination plant or the produced water salts, whether in excess or deficiency

Complete readings of the station are taken (pressures, salts, amps of wells, feeding pumps, checking voltages and Hertz for high-pressure pumps, and feeding water temperature for seawater stations). These readings are compared to the station readings before the problem occurred. Monitor the readings that have increased or decreased and make an analysis of these readings. The breakdowns are summarized as follows:

Feeding pumps

The first problem

There is a leak in the connections or gaskets at the head of the well or the feeding line or the presence of a cut in the Well Master or a leak in the well couplings and pump stages.

Indications

Low pressures of the station as a whole, especially the inlet pressure of the sand and cotton filter. The lower the productivity, the higher the water salts produced. You will also find a decrease in the flow rate of the feed water on the PLC panel. You may find no change or decrease in the amperage of the well pump.

The solution

See your line manager, fix the connections and gaskets. Or contact the projects department if the problem calls for it. Or contact the Well Department to inspect the well parts. If there is no problem with the lines and connections.

The second problem

Damage to the well pump stages or the presence of sand or gravel inside.

Indications

Decreased pressure of the plant as a whole, especially an inlet pressure of the sand and cotton filter, decreased productivity, and increased product salts. You will also find a decrease in the flow rate of the feed water on the PLC panel. And an increase in the ampere of the well pump from its normal rate.

The solution

See your line manager and contact the Well Department to investigate the problem.

Third problem

The presence of reverse pressure on the well pump.

Indications

Decreased pressure of the plant as a whole, especially the inlet pressure of the sand and cotton filter, decreased productivity and increased product salts. You will also find a decrease in the flow rate of the feed water on the PLC panel. And an increase in the ampere of the well pump from its normal rate.

The well amp decreased slightly with an increase in the inlet pressure of the sand or cotton filter and a decrease in their exit pressures.

The solution

It may be the result of a partial locking of the stopcock at the head of the well. Or entering another well on the same feeding line. Therefore, see your direct manager, and adjust the opening of the well stop or the feed pump.

The sand filter needs backwashing or the cotton filter needs to be changed.

High-pressure pump problems in RO plant

The first problem

Damaged or worn high-pressure pump stages.

Indications

The turbine pressure rises above its normal level, the pressure of entering the membranes decreases, and the H.P.P. Usually, there is a noticeable change in the voice.

The solution

Calculate the efficiency of the H.P.P and monitor the wear temperature carefully. Report to your line manager and stop the station so the damage does not increase.

The second problem

Damage to the turbine parts

Indications

Low turbine exit pressure and higher H.P.P pressure than its normal level. The pressure of entering the membranes decreases, and a decrease in H.P.P amperes may occur as a result of the reverse pressure from the turbine.

The solution

Calculate the efficiency of the turbine and inform your line manager, and stop the plant so that the damage does not increase.

Third problem

Low turbine pressure and H.P.P

Indications

It is usually the result of a decrease in the amount and pressure of the feed water. Or as a result of increased pressure on the sand or cotton filter or low voltage.

The solution

Calculate the competencies, check the filters and report to your line manager.

Fourth problem

High pressure turbine and H.P.P

Indications

It is usually the result of dirt or crusting on the membranes. It is accompanied by a high ∆P over the membranes. and output and H.P.P . amps

The solution

Check HZ&rpm and report to your line manager.

Fifth problem

PX sound higher than normal.

Indications

Increasing the amount of feed water than the need for PX (accompanied by a decrease in the H.P.P inlet pressure)

Low pressure LP out

Not completely expelling the air from the station and PX unit

Damage to the PX rotor

Replace the high-pressure terminals for the low-pressure location of the PX unit during its installation

The solution

Make sure the LP out is compressed and set to its normal level. Open the exhaust valves and make sure that there is no air inside the station. Notify your line manager.

Sixth problem

High pressure entering and exiting membranes.

Indications

High recovery (usually accompanied by an increase in production)

Increasing mixing due to an increase in the amount of water leaving the membranes than the amount entering the PX (is accompanied by an increase in salts entering the membranes and salts of the product and a decrease in production

Boost pump problem.

The solution

Calculate the recovery and mixing and compare the values ​​to their normal rates. And control the PX inlet and outlet valves to adjust pressures to normal levels.

If the pressure of the inlet diaphragms is too high than the average, it means that there is a malfunction of the rotor or the booster pump, so stop the station immediately and inform your manager.

Problems related to feeding water

The first problem

High salts of feed water

Indications

An increase in the pressure of the station as a whole.

Decreased production and increased product salts.

May cause an increase in P on the membranes as a result of desquamation if neglected.

The solution

Watch the station readings carefully and inform your line manager to check the water, and adjust the sediment injection rate.

Make sure to rinse the station with well-produced water.

The second problem

Low-temperature feed water for sea plants.

Indications

Reduced production and product salts and a slight increase in station pressures.

The solution

Monitor the temperature hourly, calculate the average at the end of the day, and report the results to your line manager for analysis.

Third problem

Increased SDI or presence of sand and turbidity.

Indications

Sand and cotton filter clogging speed.

Repeated backwashing of the sand filter, which leads to instability of pressures and production.

Damage to films and equipment may occur due to the presence of a large amount of sand.

The solution

Do a sand filter backwash in perfection.

Check the cotton filter and make sure that it is in good condition and that the wax is well attached and clean the sand carefully so that it does not enter the station.

Report to your direct managers for filters, membranes and SDI metering.

Membranes related problems in the Ro plant

The first problem

Biocontamination or Natural Organic Materials (NOM)

Indications

Production decreases with stable product salts and an increase in ∆P on the membranes.

The solution

Notify your line manager to do chemical cleaning, sanitizing or wetting the membranes.

The second problem

Colloidal contamination (eg sand and some organic matter), metal oxide contamination (eg iron, manganese) or scaling.

Indications

Production decreases with increasing product salts, and an increase in ∆P on the membranes.

The solution

Notify your line manager.

Stop the station and rinse the station thoroughly with non-chlorine producing water.

Third problem

membrane pressure

Indications

Production decreases as product salts decrease and ∆P on the membranes may decrease first.

The solution

Check the temperature of the feedwater, if the station is running directly on seawater. As the symptoms are similar to a low temperature.

Notify your line manager to investigate the problem.

Fourth problem

organic pollution

Indications

Production decreases with lower product salts and an increase in ∆P on the membranes.

The solution

Notify your line manager.

Stop the station and rinse the station thoroughly with non-chlorine-producing water.

Fifth problem

Membrane oxidation or mechanical damage.

Indications

Increased production, product salts, and decreased membrane entry and exit pressure.

The solution

Inform your direct manager.

Stop the station and rinse the station thoroughly with non-chlorine-producing water.

Sixth problem

O-ring or leakage membrane fitting

Indications

Increased product salts with stable production in the reverse osmosis plant.

The solution

Measure the salts of the pressure vessels, and do a probing test for vessels that give high readings.

Notify your line manager, stop the station and replace the damaged parts inside the pressure vessel.

Seventh problem

Membrane reduction.

Indications

Increased product salts with stable production.

The solution

Notify your line manager to inspect the membranes.

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